I am testing my well pump gpm for a sprinkler system. I have a 10 gpm 3/4 hp pump. The well is about 110' deep. I cant find anything on my pressure tank to tell me how big it is (wellxtrol model wx-203). I have a 1" line coming in my basement. I piped a 1" out of the house. When I turned the water on my pressure gage showed it holding at about 22-23 psi for about 30 seconds then it shut off and just the pump ran. I still got about 12 gpm. What does this mean? What kind of psi would the pump give me and how can I test it. Or is it because there is no back pressure or resistance my pressure tank cant build up pressure?